The present invention relates to an electrode whose front side is fitted with channel-forming threads, a method of producing an electrode, an electrolytic cell comprising an electrode according to the invention, and the use of such an electrode in electrolysis.
In electrolytic processes, the electric current is in many cases a predominant item of expenditure, and therefore a reduction of every unnecessary resistance in the electrolytic cell is desired. For example, the distance between the anode and the cathode should be as short as possible, without interfering with the flow of the electrolyte. For optimum utilisation of the material in electrolytic cells, also the surface of the electrodes in relation to the volume thereof should be as large as possible.
In many processes gas develops, which means that accumulation of gas bubbles between the anode and the cathode must be prevented so as not to increase the cell resistance. In some processes it is also common practice to separate the anode chamber and the cathode chamber by an ion-selective membrane arranged between the anode and the cathode, like in, for example, the production of chlorine and alkali. Chlorine gas forms at the anode, and to be able to fully utilise the front side of the anode for the electrolysis, the electrolyte should be able to flow freely along the anode surface. Therefore, the membrane should not engage the anode too closely, at the same time as it should be as close as possible to be able to minimise the distance between the anode and the cathode. Moreover, the electrolysis is generally carried out under excess pressure in the cathode chamber, which presses the membrane against the anode surface. These problems are difficult to solve, since available ion-selective membranes are very thin and mechanically yieldable, at the same time as they are most fragile and easily damaged when subjected to mechanical stress.
The above-mentioned problems are dealt with in EP 415,896 relating to an electrode whose front side is embossed with circulation channels for the electrolyte which are not clogged even if the membrane engages the electrode.
In many cases, modern electrodes are formed with a catalytic coating in order to optimise the desired reactions. A problem which then arises is that the catalytic activity is gradually lost in the surroundings which in many cases are corrosive. This problem is taken care of in FR 2,606,794 which suggests that the electrodes comprise a base structure and a thin net which is point-welded to the base structure and can readily be replaced when its catalytic activity has become unsatisfactory. A similar solution is suggested in BE 902,297.
DE patent 2538000 discloses a bipolar electrode construction comprising a base plate and a grid-like electrode. The electrode is not intended for use in memory brane cells.